The invention relates to antennas in general, and more particularly to antennas for radiating waves with orthogonal states of polarization.
There is a significant class of applications which require the transmission and reception of radiation characterized by two orthogonal states of polarization or linear combinations thereof. For example, in communication systems with narrow bandwidth requirements the number of communication channels may be doubled by utilizing the two orthogonal polarization states present at each frequency as carriers. Also, many electronic warfare applications require duplication of the polarization state of received signals.
Prior art dual-mode antennas generally combine orthogonal linear modes of polarization. However, for applications utilizing circular polarization, such as rain clutter reduction, it is more efficient to generate the circular modes directly. Prior art waveguide antennas capable of simultaneously emitting radiation in both circular polarization states exist, but these antennas are generally characterized by low dimensional tolerances and by narrow bandwidths.